Quick q's

Ok, so I have some general questions that should be easy to answer..

I have a 2001 SS, the dash board says Limited Edition, the car has every option available except the engine block heater.. Black w/silver, black leather interior..

Im interested in performance only modifications. From experience, what is the best of the following for my car, and give a link to a site so I can purchase if you can..

Best shift kit for car..
Best chip for computer..
Best complete exhaust (headers, cat, mufflers, pipe - bolt on if possible)
Best minor suspention modifications to enhance the lean on turns..

Also, what model transmission should I have, I checked spec sheets and they are all vague with 4speed automatic...
Thanks alot in advance...
I can be reached at [email protected]